We have obtained two procaspase 3 activators (PAC-1 and sPAC-1) from our collaborators at the University of Illinois, and have obtained a panel of cell lines on which to test the compounds with and without X-irradiation. Initial experiments with a number of sarcoma cell lines showed that they did not form discrete colonies when plated at low density, indicating that the gold standard evaluation of the effects of radiation (colony formation assay) could not be applied directly. We have evaluated several other assays based on phosphorylated gamma-H2AX histone proteins to quantitate the effect of radiation in both the absence and presence of procaspase 3 activators. We are currently validating these assays for each sarcoma cell line. We plan to continue forward and evaluate the panel of cell lines for any supra-additive effects of radiation and procaspase 3 activator drug in the near future.